Comparing NXDN, DMR, P25 We are looking forward to a presenta- tion by Steve Clark, KC6FEW, at an up- coming OCRACES meeting on the ZUMspot digital hotspot, which, like other hotspots, is essentially a personal digital voice repeater and gateway. The ZUMspot RPi Nextion 2.4 Kit sold by Ham Radio Outlet supports DMR, P25, D-STAR, Sys- tem Fusion, NXDN, and POCSAG. Some of you might not be familiar with all of these digital modes. In this article I will focus on NXDN, plus some comments about DMR and P25. NXDN NXDN stands for “Next Generation Digital Narrowband.” It is a digital narrow- band trunked radio proto- col developed jointly by Kenwood and Icom. It is used in commercial, business and industry, transportation, and public- safety professional radio systems, but rare- ly by radio amateurs. NXDN uses Frequency Division Multi- ple Access (FDMA), employing a 4-level FSK modulation scheme similar to Yaesu’s System Fusion, but the two modes are not compatible. Kenwood calls theirs “NEXEDGE” and the Icom brand is “IDAS” (Icom Digital Advanced System). An NXDN channel is either 12.5 kHz or 6.25 kHz wide. A 6.25-kHz dual- channel system can be configured to fit within a 12.5 kHz channel, effectively dou- Captain’s Corner by RACES Captain Ken Bourne, W6HK, Chief Radio Officer Newsletter of the County of Orange Radio Amateur Civil Emergency Service Orange County Sheriff’s Department Communications & Technology Division Inside this issue: Captain’s Corner 1 OCRACES Meeting 3 Coronavirus 3 Repeater Operation 3 ACS Radio Rodeo 4 EOC Training 4 Cooperative T-Hunt 5 PSR Orientation 5 RACES/MOU News 6 Events Calendar 7 OCRACES Members 8 County of Orange RACES NetControl bling the spectrum efficiency compared to an analog FM system occupying a 12.5 kHz channel. Two NXDN channels within a 12.5 kHz channel can be allocated as voice/voice, voice/data, or data/data. There are two main modes, NXDN48 and NXDN96. NXDN48 bandwidth is 6.25 kHz, symbol rate is 2400 baud, data rate is 4800 bps, with two FDMA channels per 12.5-kHz channel, speech code rate is 3600 bps, and C4FM frequency deviation is ±1050 Hz, ±350 Hz. NXDN96 bandwidth is 12.5 kHz, symbol rate is 4800 baud, data rate is 9600 bps, with one FDMA channel per 12-kHz channel, speech code rate is 3600 bps (7200 bps option), and C4FM frequency deviation is ±2400 Hz, ±800 Hz. Kenwood’s NXDN radios are an ITU- R accepted Common Air Interface (CAI) NEXEDGE digital two-way radio system. Enhanced Mixed Zone allows any digital CAI and/or FM analog to reside in the same zone. Zone scan automatically sets all users in the same zone in the same RX/TX mode. The NX-5000 and NX-3000 Series radios are able to communicate in analog, NXDN, DMR, and P25 formats. A few years ago, the FCC forced exist- ing commercial users to “narrowband,” transitioning from 25 kHz bandwidth to 12.5 kHz. But that was just a stepping stone to 6.25 kHz, which is incompatible with analog voice. Two technologies evolved from this—one based on TDMA (Time Division Multiple Access) and the other on FDMA (Frequency Division Mul- tiple Access). Those two technologies are not compatible with each other. Next OCRACES Meeting: Monday, March 2, 2020, at 1930 Hours 840 N. Eckhoff Street, Suite 104, Orange John Pilger, K6PIO: Maricopa County Sheriff’s Communica- tions Posse
8
Embed
County of Orange RACES NetControlTier II is conventional (as used by radio amateurs) and Tier III is trunked. Data throughput is similar to P25 Phase 2, at 9600 bps (symbol rate of
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Transcript
Comparing NXDN, DMR, P25
We are looking forward to a presenta-
tion by Steve Clark, KC6FEW, at an up-
coming OCRACES meeting on the
ZUMspot digital hotspot, which, like other
hotspots, is essentially a personal digital
voice repeater and gateway. The ZUMspot
RPi Nextion 2.4 Kit sold by Ham Radio
Outlet supports DMR, P25, D-STAR, Sys-
tem Fusion, NXDN, and POCSAG. Some
of you might not be familiar with all of
these digital modes. In this article I will
focus on NXDN, plus some comments
about DMR and P25.
NXDN
NXDN stands for “Next Generation
Digital Narrowband.” It is a digital narrow-
band trunked
radio proto-
col developed
jointly by
Kenwood and
Icom. It is used in commercial, business
and industry, transportation, and public-
safety professional radio systems, but rare-
ly by radio amateurs.
NXDN uses Frequency Division Multi-
ple Access (FDMA), employing a 4-level
FSK modulation scheme similar to Yaesu’s
System Fusion, but the two modes are not
compatible. Kenwood calls theirs
“NEXEDGE” and the Icom brand is
“IDAS” (Icom Digital Advanced System).
An NXDN channel is either 12.5 kHz
or 6.25 kHz wide. A 6.25-kHz dual-
channel system can be configured to fit
within a 12.5 kHz channel, effectively dou-
Captain’s Corner by RACES Captain Ken Bourne, W6HK, Chief Radio Officer
Newsletter of the County of Orange Radio Amateur Civil Emergency Service
Orange County Sheriff’s Department Communications & Technology Division
Inside this issue:
Captain’s Corner 1
OCRACES Meeting 3
Coronavirus 3
Repeater Operation 3
ACS Radio Rodeo 4
EOC Training 4
Cooperative T-Hunt 5
PSR Orientation 5
RACES/MOU News 6
Events Calendar 7
OCRACES Members 8
County of Orange RACES
NetControl
bling the spectrum efficiency compared to
an analog FM system occupying a 12.5
kHz channel. Two NXDN channels within
a 12.5 kHz channel can be allocated as
voice/voice, voice/data, or data/data.
There are two main modes, NXDN48
and NXDN96. NXDN48 bandwidth is 6.25
kHz, symbol rate is 2400 baud, data rate is
4800 bps, with two FDMA channels per
12.5-kHz channel, speech code rate is 3600
bps, and C4FM frequency deviation is
±1050 Hz, ±350 Hz. NXDN96 bandwidth
is 12.5 kHz, symbol rate is 4800 baud, data
rate is 9600 bps, with one FDMA channel
per 12-kHz channel, speech code rate is
3600 bps (7200 bps option), and C4FM
frequency deviation is ±2400 Hz, ±800 Hz.
Kenwood’s NXDN radios are an ITU-
R accepted Common Air Interface (CAI)
NEXEDGE digital two-way radio system.
Enhanced Mixed Zone allows any digital
CAI and/or FM analog to reside in the
same zone. Zone scan automatically sets all
users in the same zone in the same RX/TX
mode. The NX-5000 and NX-3000 Series
radios are able to communicate in analog,
NXDN, DMR, and P25 formats.
A few years ago, the FCC forced exist-
ing commercial users to “narrowband,”
transitioning from 25 kHz bandwidth to
12.5 kHz. But that was just a stepping
stone to 6.25 kHz, which is incompatible
with analog voice. Two technologies
evolved from this—one based on TDMA
(Time Division Multiple Access) and the
other on FDMA (Frequency Division Mul-
tiple Access). Those two technologies are
not compatible with each other.
Next OCRACES
Meeting:
Monday,
March 2, 2020,
at 1930 Hours
840 N. Eckhoff Street,
Suite 104, Orange
John Pilger, K6PIO:
Maricopa County
Sheriff’s Communica-
tions Posse
Page 2 March 2020
TDMA transmissions (such as DMR) have 12.5 kHz
bandwidth, but two groups can transmit at the same time,
effectively creating two equivalent 6.25 kHz channels.
FDMA transmission bandwidth is 6.25 kHz. Multiple
transmissions are divided by being on different frequen-
cies.
NXDN supports the European dPMR (Digital Private
Mobile Radio) standard but does not comply with all as-
pects of it.
NXDN complies with FCC requirements for 6.25
kHz channel equivalence. In the commercial market, cost
is relatively low compared with other digital modes. It is
backwards compatible with analog and with LTR (Logic
Trunked Radio) networks. NXDN is commonly thought
to sound better than DMR. Trunked NXDN products
from different manufacturers (such as Kenwood and
Icom) are not compatible with each other, but trunking is
not an issue in amateur radio. Portable battery shift life is
shorter than with DMR radios, due to the FDMA trans-
mission format compared with DMR’s TDMA transmis-
sions that 27.5 ms long every 60 ms. NXDN FDMA tech-
nology is also outdated and proprietary.
Amateur repeaters using NXDN are rare. The only
one I see listed in California on RepeaterBook is
WA6YLB on 443.500 MHz (+) in Visalia.
DMR
DMR operates in 12.5
kHz channels and uses 2
slot TDMA to achieve
6.25 kHz equivalence.
Tier II is conventional (as
used by radio amateurs)
and Tier III is trunked. Data throughput is similar to P25
Phase 2, at 9600 bps (symbol rate of 4800 symbols per
second). With 4FSK modulation, there is no need for lin-
ear transmitters and cost is about the same as analog FM
transmitters. Coverage is about the same as analog FM.
DMR is a non-proprietary open standard. TDMA
extends radio battery life when compared with 12.5 kHz
analog FM radios or P25 Phase 1 radios. However, it
does not provide full-duplex operation.
Both DMR and dPMR/NXDN/NEXEDGE/IDAS
appear to achieve one communications path per 6.25 kHz
of spectrum. However, Tait Communications points out
that, in the case of an emergency, when you need the ra-
dio system the most, dPMR/NXDN/NexEdge will suffer
increased interference, which means a user can only reli-
ably use every other 6.25 kHz channel. Tait says DMR
will achieve one communications path per 6.25 kHz of
spectrum, irrespective of loading, twice the capacity of
analog narrowband FM. Despite Tait’s touting of DMR
over NXDN, it has an impractical aspect for amateur use.
In a typical DMR repeater system, several talkgroups
exist on each time slot. A typically long ham conversa-
tion (compared to shorter communications on commer-
cial channels) will tie up one DMR time slot so that other
talkgroups on that time slot are unusable at the time. If
there is a pause in the conversation, someone on another
talkgroup might “hi-jack” the time slot and the original
conversation will be disrupted or lost. That problem can
be overcome through the use of a hotspot, such as the
ZUMspot that Steve Clark, KC6FEW, will talk about at
an upcoming OCRACES meeting.
P25
P25 is a common format
in commercial and public-
safety radio systems, but
there are very few P25 ama-
teur radio repeaters. The
original P25 Phase 1 uses a
C4FM modulation scheme
(similar to Yaesu’s System Fusion, but not compatible).
Data throughput is similar to DMR. There is no need for
linear transmitters; thus, cost and size are about the same
as an analog transmitter. Transmitter output spectrum fits
into existing 12.5 kHz narrowband FM analog channels.
P25 Phase 2 is a 2-slot TDMA system. It has a lower
data throughput than TETRA (a European standard for a
digital trunked radio system) at 12,000 bps (symbol rate
of 4800 symbols per second). Modulation schemes are
intended to optimize performance and simplify terminal
design. It uses HDQPSK modulation in the downlink
(base station to terminals), requiring a more expensive
and larger linear base-station transmitter. Transmitter
output spectrum fits into existing 12.5 kHz narrowband
FM analog channels.
P25 is a non-proprietary open standard, designed par-
ticularly for public safety. It provides conventional,
trunked, and simulcast options, including combinations
of these options. Equipment can operate in analog FM
mode, in digital P25 mode, or in dual mode. It supports
simplex mode (repeater talkaround) for direct communi-
cations outside network coverage. It also allows secure
end-to-end encryption (not legal for amateur radio com-
munications). Phase 1 provides only 12.5 kHz channel
OCSD Emerg. Comm’s Coordinator Pete Jimenez, KI6UTE, 714-704-8080 OCSD Sr. Telecommunications Engr. Erik Schull, KE6BVI, 714-704-7937 Chief Radio Officer (Captain) Ken Bourne, W6HK, 714-997-0073
Radio Officer (Lieutenant) Scott Byington, KC6MMF Assistant Radio Officers (Sergeants) Jack Barth, AB6VC Ernest Fierheller, KG6LXT Bob McFadden, KK6CUS Tom Tracey, KC6FIC
• March 2: OCRACES Meeting, 1930 hours, 840 N. Eckhoff Street, Suite 104, Orange
• March 14: Sworn Reserve Meeting, 0800-1200 hours, and PSR General Membership Meeting, 1000-1430 hours, Sheriff’s Regional Training Academy, Tustin
• March 16: Cooperative T-hunt, 1920 hours
• March 20: Orange County Amateur Radio Club (OCARC) Meeting, 1900 hours, American Red Cross (George M. Chitty Building), 600 Parkcenter Drive, Santa Ana
• April 4-5: Baker to Las Vegas Chal-lenge Cup Relay
• May 2: ACS Radio Rodeo, 0830-1100 hours, 840 N. Eckhoff Street (rear parking lot), Orange
• June 8: City/County RACES & MOU Meeting, 1930 hours, 840 N. Eckhoff Street, Suite 104, Orange
• June 27-28: ARRL Field Day
• July 11: HRO Ham Jam
March 2020 Sun Mon Tue Wed Thu Fri Sat
1 2 Weekly 2 m ACS Net & OCRACES Meeting
3 4 5 6 7 Weekly 60 m ACS Net
8 9 Weekly 2 m ACS Net
10 11 12 13 14 PSR Meeting (no net)
15 16 Weekly 2 ACS Net & Cooperative T-Hunt
17 18 19 20 Orange County Ama-teur Radio Club Meeting